DNS DEMYSTIFIED

How do I locate www.iisc.ernet.in from cyber cafe in Beijing

Domain Naming Service (DNS), an Internet protocol and distributed database, provides the mapping between disparate addresses, one numeric address and the other user friendly addresses like csa.iisc.ernet.in . Having a basic understanding of how DNS works is key to successfully administering an Internet-connected network.

First we need to take a quick look at the structure of Internet host names. Computers connected to the Internet have unique numerical addresses called as IP (Internet Protocol) addresses, so that the electronic information gets delivered to the right place on the Internet. Domain Names are the familiar, easy to recall names for the computers on the Internet. They are used generally as a convenient way for the human beings
to locate information on the Internet. The Domain Name System (DNS) translates these domain names to the IP addresses of the computers. Thus, a domain name such as search.msn.co.in should map onto an IP address such as 207.46.176.53.The last portion of a host name, such as .com, is the top-level domain to which the host belongs. In addition to the .com domain, there are six other top-level domains assigned by InterNIC, the coordinating body for Internet name services.

TLDs

There are two types of Top-Level domains (TLDs), generic and country code. Generic domains were created for use by the Internet public, while country code domains were created to be used by each individual country as they deemed necessary. The generic TLDs (gTLDs) are COM, ORG, NET, EDU, GOV etc and the country codes TLDs (ccTLDs) like IN, UK, JP, US etc are 2-letter country codes maintained by the ISO 3166 Maintenance Agency.

How do I locate www.iisc.ernet.in from cyber cafe in Beijing

When the computer attempts to resolve a name to an IP address, it first looks in its local cache for the answer. If it's not there, the computer will ask the DNS server of the ISP "what's the ip address of www.iisc.ernet.in'?". The ISP's DNS server will look in its list of recent answers and send the answer to my computer if it's in the cache. If not, the ISP's DNS server will start asking around to find out.

What most people don't know is that a "fully" qualified domain name (FQDN) actually ends with a period. The period is the root. The root servers tell other DNS servers where to find the TLDs (top level domains). So the real URL is "http://iisc.ernet.in." for those who like to be exact. At the top of the DNS database tree are root name servers, which contain pointers to master name servers for each of the top-level domains. If the ISP's DNS server knows the DNS server for iisc.ernet.in, it'll ask that DNS server "what's the IP address for http://iisc.ernet.in.?" If it doesn't know the DNS server for iisc.ernet.in., it will attempt to find the DNS server for ernet.in.. If it can't find that, it'll try to find the DNS server for in. (the top level domain). If it can't find the DNS server for in., it'll go to the DNS server for "." (the root). There are 13 of those servers located throughout the world. They point to the DNS servers for com., edu., uk., and all the other top level domains.

At the top of the DNS database tree are root name servers, which contain pointers to master name servers for each of the top-level domains. For example, to find out the numeric address of www.iisc.ernet.in, a DNS server would ask the root name server for the address of the master name server for the ccTLD (country codes TLDs) domain.

In turn, the master name servers for each of the top-level domains contain a record and name-server address of each domain name. So in trying to find out the numeric address of www.iisc.ernet.in the DNS server asks the ccTLD server for the name of the server that handles the ernet.in domain.

Why DNS server on your LAN

Firstly, if you are running IP network-based applications inside your network that require users to connect to internal machines by name, it is not a great idea to advertise the names and addresses of these machines. DNS can give hackers a map of your network, so setting up an internal DNS server that does not publish information to the world is a good idea.

Secondly, a DNS server inside your network lets you be the master of your own domain. You can make changes, additions, and deletions on your own schedule.

Finally, name resolution will be faster for your users because your DNS server is probably not as heavily loaded as your ISP's server.

Register domain name in INDIA

National Centre for Software Technology (NCST),a scientific R & D institution under the Ministry of Information Technology(MIT),Government of India is the ccTLD Manager for the IN country code top-level domain(ccTLD). NCST has been registering domain names under IN domain name space since 1995.

The Internet Management Group(IMG), a committee formed by the Govt. of India, oversees the Internet domain name registration related activities for the IN ccTLD.

This committee consists of members representing

Bharat Sanchar Nigam Ltd(BSNL)
Ministry of Information Technology(MIT)
Videsh Sanchar Nigam Ltd(VSNL) and
National Centre for Software Technology (NCST)